In general, minute patterns, which are used in semiconductor circuit elements and display devices such as an LCD and a PDP, are formed by photolithography using a photoresist, and generally manufactured by performing a coating step, an exposure step, a developing step, a cleaning step, and a curing step.
However, even though the photolithography has an advantage in that desired and precise patterns may be obtained, the photolithography has drawbacks in that a number of processes need to be performed, numerous types of materials need to be used to maximize the effect of the photoresist, and a large amount of photoresist is consumed in a process such as a coating process.
In recent years, in order to resolve the drawbacks of the photolithography, researches and developments are conducted on a technology that is suggested to obtain minute patterns using a roll printing manner.
The roll printing apparatus for forming patterns may be applied to various manners such as offset printing, reverse offset printing, and roll-to-roll printing, and may be applied to a wide field to transfer patterns such as patterns for forming electrode of a thin film transistor (TFT) or a plasma display panel (PDP), and patterns of barrier rib materials as well as R (Red), G (Green), B (Blue) colors, which are constituent elements of a color filter, and black matrix (BM) patterns.
The roll printing apparatus generally comprises a coater, a printing roll, a printing roll drive device, a cliche, or a drive device for alignment of a substrate stage and a stage as mostly basic constituent elements, and may additionally comprise a cliche and/or piping cleaning device, a drying device for drying a blanket by absorbing solvent absorbed in the blanket, and various types of sensors.
Precision of the pattern formed by the roll printing manner and pattern transfer efficiency greatly depend on process conditions such as a coating state from the coater to the roll or the blanket of the roll, an amount of volatilized solvent and a standby time until the pattern is transferred to the cliche or the substrate after a coating process, and printing pressure that is formed by a gap between the stage and the roll or the blanket while the pattern is transferred.
Particularly, by the coating state at the time of coating the roll or the blanket, which is a first step of the roll printing process, whether stains having various shapes are formed or not as well as uniformity of the entire patterns are determined.
In general, according to the roll printing apparatus as described above, there is a drawback in that the a tack time is inevitably required until a printing process is performed by preparing the printing roll again and coating the printing roll after one printing process is performed using the printing roll.
Here, the tack time means the time taken until a subsequent glass substrate is loaded after one product is unloaded, the tack time is set by adjusting the number of other apparatuses on the basis of the time taken until the glass substrate is unloaded from photolithography equipment after the glass substrate is loaded in the photolithography equipment when the liquid crystal display (LCD) is manufactured, and even in the case of the printing roll, the tack time similarly means the time taken when one printing roll is moved in and out. In the case of the roll printing, there is a limit in that a production speed is relatively low because of the tack time in comparison with the photolithography equipment.